1. Field of the Invention
This invention relates to a transmissive display device with an active matrix structure, having a driving substrate, a counter substrate, and liquid crystal held therebetween. In particular, this invention relates to a so-called on-chip black structure in which there is formed a black matrix for shielding light, as well as pixel electrodes and switching devices, on a driving substrate.
2. Description of the Related Art
Liquid crystal display devices are widely used in televisions, graphic displays, and so forth. Among them, in particular, an active-matrix type liquid crystal display apparatus has high speed responsibility and is suitable for having an increased number of pixels, and has been anticipated and researched in order to realize enhanced quality of a display screen, an enlarged size of the screen, a multi-colored display, and so on, and as a result, there already has been achieved a practical example. As shown in FIG. 5, this active matrix type liquid crystal display apparatus has a driving substrate on which a scanning bus line pattern and a signal bus line pattern are formed perpendicular to each other. Switching devices 102 and pixel electrodes 103 are formed respectively at points where both patterns intersect with each other. On the other hand, on a counter substrate 104, there is ordinarily formed a black matrix 106 as well as a counter electrode 105. This black matrix shields incident light from the counter substrate 104 to prevent switching devices 102 from malfunctioning due to photoelectric currents, while the matrix shields leaked rays passing between the pixel electrodes 103 arranged in a matrix to prevent deterioration of contrast. Between the driving substrate 101 and the counter substrate 104, liquid crystal is provided. However, providing the black matrix 106 on the counter substrate 104 requires fine alignment with the driving substrate 101, which thus creates difficulties in assembly. As a countermeasure against such a difference in alignment, a method is generally used wherein a black matrix is provided so as to overlap to some extent with the respective pixel electrodes 103. With this method, it is possible to reduce an alignment error caused by putting together the driving substrate 101 and the counter substrate 101, to the size of an overlapping part. However, providing an overlapping part causes a reduction of the aperture area of the black matrix 106 with respect to the pixel electrode 103 by the amount of such overlap, so that the aperture ratio deteriorates and reduces the brightness of the pixel. The black matrix 106 is formed of, e.g., a metallic layer with light-shielding properties, and to some extent reflects incident light. The reflected light is repeatedly reflected on the counter substrate 104 and so forth, a part of which travels into the liquid crystal 107.
As described above, a black matrix provided on a counter electrode causes a problem in that a difference in alignment occurs when a driving substrate and a counter substrate are joined together. To this end, there has been proposed a so-called on-chip black structure formed by providing the black matrix on the driving substrate. On the same substrate, it is possible to realize alignment precision between a pixel electrode and a black matrix, up to approximately 1 .mu.m. Such an on-chip black structure is disclosed in, e.g., Japanese Patent Laid-Open Publication No. 5-181159, which is schematically shown in FIG. 6. Parts that correspond to those in an embodiment shown in FIG. 5 are denoted by the corresponding reference numerals, so as to be readily understood. However, since the on-chip structure has a black matrix 106 formed by, e.g., a metallic layer, and provided on a matrix array substrate 101, and has no light-shielding layer on a counter substrate 104, a problem arises such that multiple reflection occurs, so that contrast deteriorates. As described above, since the black matrix 106 is formed by a metallic layer, it reflects incident light at a certain ratio. A reflection layer provided on the matrix array 101 creates light components that are repeatedly reflected in liquid crystal 107. The multiple reflection light in the liquid crystal 107 has a different polarization plane from normal light passing through the liquid crystal only once, and as a result, even in the case of displaying black, leaked rays appear, so that contrast deteriorates. In particular, in a region in which there is a reverse tilt domain caused by a lateral electric field, multiple reflection causes a great amount of leaked rays. Multiple reflection occurs in connection with not only incident light from the counter substrate 104 but also incident light from the matrix array 101, which thus affects contrast.